Flowering Question

Okay so today was the autumnal equinox, which means days are now 12 hours of light, 12 hours of darkness. So why then, has my outdoor plant begun flowering a couple weeks before the autumnal equinox? It's not an autoflowering strain btw

A plant doesn't need a solid 12 hours of darkness to start flowering, it's just the ideal timer setting for an indoor flowering room. The plants were triggered into flowering when they received enough hours of darkness to let them know that the end of their life was imminent.

12 hours is a number indoor growers use to trigger flowering. plants naturally begin to flower after the point in which the days start getting shorter. a jump from 18-12 just sends a signal to the plant it's time to begin flowering.